Publications and other reference materials referred to herein, including references cited therein, are incorporated herein by reference in their entirety and are numerically referenced in the following text and respectively grouped in the appended Bibliography, which immediately precedes the claims.
Molecular electronics and optoelectronics [1–4] have been gaining prominence over the past few years. Development in these fields has been restricted, however, since organic molecules are commonly optically active only at wavelengths shorter than 1 μm. Previous attempts to achieve ‘plastic’ based light emitting devices beyond 1 μm involve the incorporation of lanthanide complexes. In these complexes, a rare-earth atom is placed within an organic molecule [5, 6, 7]. The most obvious choice is that of the Erbium atom, which is the common amplifying medium employed in the 1.5 μm telecommunication range.
To date, such attempts have suffered from absorption bands (associated with the vibrations of the organic-molecule or polymer) that deactivate any lanthanide atom that has been tried. Methods that attempt to shield the lanthanide have been developed [8], but there still remains much room for improving the obtained results in terms of: intensity, efficiency, wavelength coverage, and spectral bandwidth. For example, the reports of the results of the work done with the lanthanide complexes show extremely small efficiency and wavelength coverage as dictated by the discrete lanthanides atomic lines.
The inherent and proven qualities of organic light-emitting molecules and polymers in the visible range [2, 9, 101 are the driving force behind the quest for extending the plastic technology to the near infrared (NIR), where the telecommunication bands are located around 1.3 μm and around 1.5 μm.
Nanocomposite devices in which core/shell nanocrystals are incorporated within a conducting polymer have been previously demonstrated for the visible range [11–14], but have not yet been reported for the NIR.
The use of core/shell [11–19] semiconducting nanocrystals and, in particular those with strong emission in the NIR [4, 201, is well known. Co-pending International Patent Application WO 02/25745, the description of which is incorporated herein by reference, describes in detail NIR emitting core/shell nanocrystals.
It is therefore, a purpose of this invention to provide composite materials consisting of a host material in which are incorporated semiconductor nanocrystals such that the composite material efficiently emits/absorbs energy or changes its dielectric constant in the near infrared spectral range.
It is a further object of this invention to provide composite materials that efficiently emit/absorb energy or change their dielectric constant in the near infrared spectral range and can thus be used in the manufacture of electrooptical devices.
It is a further a purpose of this invention to provide electro-optical devices composed of semiconductor nanocrystals which emit/absorb energy in the NIR, mixed with or blended into a conducting or semiconducting polymer.
It is yet a further purpose of this invention to provide a method of producing electro-optical devices including light emitting diodes composed of core/shell nanocrystals incorporated within a conducting or semi-conducting polymer that efficiently emit energy in the near infra red.
It is another purpose of this invention to provide a method of applying voltage or current to a composite material composed of core/shell nanocrystals mixed with or blended into a conducting or semi-conducting polymer to construct lightdetectors or light modulators.
It is yet another purpose of this invention to provide a method of designing the nano-crystal structure so as to optimize its incorporation into the polymeric materials.
Further purposes and advantages of this invention will appear as the description proceeds.